1. Technical Field of the Invention
The present invention relates to novel 2-amino-4-alkylaminopyrimidine 3-oxide chemical compounds, to compositions comprised thereof and to the use of such novel compounds/compositions as active principles for inducing and/or stimulating hair growth and/or for preventing hair loss.
2. Description of the Prior Art
In human subjects the growth and renewal of the hair are principally determined by the activity of the hair follicles. This activity is cyclic and essentially entails three phases, i.e., the anagenic phase, the catagenic phase and the telogenic phase.
The active anergenic phase, or growth phase, which lasts for several years and during which the hair elongates, is followed by a very short and transient catagenic phase which lasts for a few weeks, and then a rest or quiescent phase, designated the telogenic phase, which lasts for a few months.
At the end of the rest period, the hair falls out and another cycle begins anew. The head of hair is thus under constant renewal, and out of the approximately 150,000 hairs on a head of hair, at any given instant approximately 10% are at rest and will thus be replaced within a few months.
However, different causes can lead to a considerable, temporary or permanent, loss of hair. Alopecia is essentially due to a disruption in hair renewal which occasions, in a first stage, an acceleration of the frequency of the cycles, at the expense of the quality of the hair and then at the expense of its quantity. A gradual depletion of the head of hair takes place by regression of the so-called "terminal" hairs at the downy stage. Certain regions are preferentially affected, in particular the temples or frontal bulbs in men, and in women, diffuse alopecia of the vertex is observed.
By the term "alopecia" are intended the entire family of afflictions of the hair follicle, the final consequence of which is the partial or general permanent loss of the hair. In a large number of cases, early loss of the hair arises in genetically predisposed individuals and especially affects men. This more particularly applies to androgenetic or androgenic or even androgeno-genetic alopecia.
Active substrates for suppressing or reducing alopecia, and in particular for inducing or stimulating hair growth or reducing hair loss, have long been considered desiderata in the cosmetics and pharmaceutical industries.
In this respect, a large number of very diverse active compounds have already been suggested for such purposes, for example, 2,4-diamino-6-piperidinopyrimidine 3-oxide or "Minoxidil" described in U.S. Pat. Nos. 4,139,619 and 4,596,812, or the many derivatives thereof, such as those described, for example, in EP-0,353,123, EP-0,356,271, EP-0,408,442, EP-0,522,964, EP-0,420,707, EP-0,459,890 and EP-0,519,819.
Nonetheless, serious need continues to exist for yet other active agents/species potentially more active and/or less toxic than those active substrates to date characterizing the state of this art.